Wrapped plain bearing bush

ABSTRACT

A wrapped plain bearing bush having a bush width which varies in the peripheral direction. The bush is characterized in that it is wrapped from a strip-shaped band section which is provided with a variable over the length of the section while still in its flat state and which is wrapped in such a way that the wrapped bush does not need to be subjected to any further cutting of the width; but, instead, has its definitive, variable bush width after wrapping on the bush mold.

BACKGROUND

The invention relates to a process for manufacturing a rolled-up plainbearing bush having a bearing width that varies over the length of thecircumference and having machined peripheral ends.

Plain bearing bushes of this type are known. Such bearing bushes areused, in particular, as connecting rod bearings in the small end of theconnecting rod in combustion engines. The varying bushing width isintended to effect a weight savings as compared to the solidlypressed-in plain bearing bushing, but are also adapted to geometricconstraints at the side.

Until now plain bearing bushings of this type have been rolled ascylindrical bushings out of a rectangular, ribbon-shaped section of astrip of the bearing material or compound bearing material. Then thebushing was brought to the desired shape by machining in equipment forwidth turning. To do this, a rotationally driveable cutting tool with anaxis of rotation set at an angle to the bushing's longitudinal axis isadvanced in an automated machine for width turning on one side or onboth sides, so that the machined peripheral ends or peripheral endsections are lying in one plane. In this way a bushing shape describedin a side view as what is known as a trapezoid can be achieved. Afterthe so-called turning to width, the outer and/or inner bevel of thebushing ends has to be formed in a very complicated manner in additionalmachining involving metal removal.

Instead of equipment for turning the bushing to width, a known finishedrolled cylindrical plain bearing bushing can also be machined by meansof a milling cutter in such a way that it has a varying bushing widthover the length of the circumference. If there should be any doubt, thisprocess is even more complicated.

With rolled-up plain bearing bushings, punching out a relatively shortrectangular recess from the material ribbon prior to the rollingprocedure was also known. As a result, a bushing with varying width overthe length of the circumference is certainly created, but machining ofthe punched out peripheral end section is not performed (see, forexample, catalogue from Jorg Vogelsang GmbH & Co. from 1990, MetalForming, page 14, Bearing Bushings).

GB-A-1 597 9604 teaches the manufacture of bushings with varying bushingwidth over the length of the circumference in pairs or in batches bydemarcating several strips immediately adjacent to each other in thetransverse direction from a single roll of flat material to produceseveral bushings. First, longitudinal sections are formed from severalbushings next to each other in the transverse direction, which are thentransferred and rolled up in the transverse direction. Only then in therolled-up state are the bushings separated. If machining of theperipheral ends is desired, this has to take place subsequently.

Starting from this, it is desirable to create a rolled-up plain bearingbushing with a bushing width varying over the length of thecircumference, which can be manufactured more economically and which hasmore uniformly machined peripheral ends than known bushings.

SUMMARY

The process according to the invention is characterized in that afterbeing rolled up, the plain bearing bushing does not have to undergo anymachining to its width involving cutting. It has accordingly a welldefined, clean side profile which, because of its rotationallynon-symmetrical geometry, could never be achieved by means of the knownmachining to its width through metal cutting and subsequent sidemachining. The person skilled in the art can recognize without anydifficulty from the finished product under the invention that thevarying bushing width over the length of the circumference was notproduced by a machining process involving metal cutting.

The plain bearing bushing under the invention, which is manufacturedfrom a previously formed ribbon-shaped section of strip, that is, aformed blank, has the advantage that the bushing can be produced in therolling-bending tool being finished without subsequent machining towidth.

An offset shape, specifically, a multiple offset shape for the bushingwidth, can be produced in a particularly advantageous way, without theneed for any metal-cutting machining to width. This is understood in themathematical sense to be a discontinuous course of the peripheral ends.But even a course of the peripheral ends which is curved in sections,i.e., one that is non-linear, can turn out to be advantageous. It waspossible to produce a shape of this type previously only by machiningusing a milling cutter.

The invention further proves to be advantageous if the side sections ofthe ribbon-shaped section of strip forming the circular peripheral endshave a coined bevel at least in sections, specifically one that is notcreated by removing metal by machining, which is introduced while stillin the planar state before the section of strip is rolled up.

According to the procedure under the invention, a ribbon-shapedcontinuous roll of flat material is fed in its longitudinal direction toa cutting device, in which the side shape forming the terminatingcircular peripheral ends is cut into the roll of flat material. What iscreated is a profile of varying width running in the longitudinaldirection. Bevels are then created along the edges of the profiled rollof flat material, preferably by means of coining. Then the sectionsforming the individual bearing bushings are separated from thecontinuous roll of flat material. These strip sections are then rolledup into the bushing shape to form the finished free-falling bearingbushing.

Preferably after cutting the side shape and before separating androlling up the sections of the strip, each of the longitudinal sides isgiven an edge, profile rolled, and, if necessary, chased. In the sameway, preferably before rolling up the strip sections, an oil grooveand/or lubricating holes can be coined or stamped. After the bushingsare rolled up, only a ball-sizing calibration and an outside drawcalibration need to be performed.

BRIEF DESCRIPTION OF THE DRAWING

Additional features, details and advantages of the invention can bederived from the attached patent claims, for whose features protectionis sought for each one taken individually. A preferred embodiment of thepresent invention is described in the ensuing with reference to theattached drawing. In the drawing:

FIG. 1 shows a plan view of a strip section in a flat state beforerolling up a bearing bushing in accordance with the invention;

FIG. 2 shows a perspective view according to FIG. 1;

FIG. 3 shows a side view of the bearing bushing rolled up from thesection of strip according to FIGS. 1 and 2;

FIG. 4 shows an end view of the bearing bushing according to FIG. 3;

FIG. 5 to 8 show views of an additional embodiment of the bearingbushing according to the invention, similar to FIGS. 1 to 4; and

FIG. 9 shows a schematic representation of a ribbon-shaped continuousroll of flat material with a suggested cut line to create two strips.

DETAILED DESCRIPTION

FIGS. 1 to 4 show an initial embodiment of a bearing bushing accordingto the invention, which is identified overall by reference numeral 2.The bearing bushing 2 is manufactured from a ribbon-shaped section ofstrip 4 of a composite metallic bearing bushing material. The section ofstrip 4 is cut from a continuous roll of flat material creating a formedblank and exhibits a varying width. On both sides the section of strip 4comprises two side sections 8, 10 running parallel to the longitudinaldirection 6 and in alignment with each other, which on one side lead tothe ends 12, 14 of the section of strip 4 and, on the other side,transition into two side sections 18, 20 running to the outside at anangle to the longitudinal direction which delineate a broader section16. These angled side sections 18, 20 are connected by a parallel sidesection 22, in turn running parallel to the longitudinal direction 6.

A tongue-shaped projection 24 and a matching recess 26 is formed on theends 12, 14 of the section 4 abutting each other in the load impactarea.

The side sections 22 running parallel to the longitudinal direction 6,delineating the broader section 16, have a bevel, which was introducedby chasing before cutting in the remaining side sections 8, 10 and 18,20 from the continuous roll.

In the case of the remaining side sections 8, 10 and 18, 20, a bevel 30,32, respectively, was formed by coining, that is, without metal removal,after the profile shape was cut. The side sections 8, 10 and 18, 20could also have a bevel formed by coining without metal cutting. Theside sections 8, 10 and 18, 20 can be given a bevel on the inside on therunning surface and/or on the outside on the backing.

FIGS. 3 and 4 show two views of the rolled up bushing 2. The varyingwidth b over the length of the circumference can be seen. The circularperipheral ends 34 in the view of FIG. 4 are formed symmetrically to thelongitudinal line 6 in the embodiment depicted here.

The bushing width defined in the load impact area by the side sections8, 10 is b1, and the width of the bushing defined by the side sections20,22 is (b). Between the side sections 8, 10 and 20, 22, the peripheralends 34 are offset twice, more precisely, at the transition of the sidesection 8 to the side section 18 and from there once more to the sidesections 20,22.

FIGS. 5 to 8 show an embodiment of a bearing bushing according to theinvention, similar to FIGS. 1 to 4, whose side sections 40, 42terminating in the load impact area at the ends 12, 14, run at an angleto the longitudinal direction 6 of the ribbon-shaped section 44. At itsother end the straight side sections 40, 42 transition into a sidesection 44 running parallel to the longitudinal direction 6. The sidesections 40, 42, 44 are machined as described in connection with FIGS. 1to 4.

The bearing bushing 48 rolled up from this section of strip 44 is offsetonce, to be precise, at the transition of the side section 46, whichdelineates a broader area 50, to the side sections 40, 42.

The bushing width varies then between a width b defined by the distancebetween the side sections 46 on both sides and a width b1 defined by thedistance of the side sections 40, 42 to the ends 12, 14.

Finally, FIG. 9 shows a schematic representation of a continuous bearingmaterial 60 as a roll of flats. The suggested arcuate line 62 identifiesa cut to create two continuous strips 64, 66 having, on one side, astraight side run 68, 70 and, on the other side, an arcuate side run 72,74. If sections of length 1 are separated from this continuous roll,rolled up bearing bushings having a bushing width varying between b andb1 over the length of the circumference can be produced, where, with thesuggested positioning of the cut line 76, the load impact area of therolled bearing bushing has the smaller bushing width b1.

The advantage of this embodiment is that no waste of any kind isgenerated by the cut. It is obvious that bearing bushes in accordancewith FIGS. 1 to 8 can also be produced from two or several continuousstrips cut in the longitudinal direction from a continuous roll.

What is claimed is:
 1. A process for manufacturing a rolled-up plainbearing bushing from a ribbon-shaped continuous roll of flat material,having a bushing width which varies over the length of thecircumference, comprising the sequential steps of: cutting a side shapefrom a ribbon-shaped continuous roll of flat material, so that a profileof varying width is formed, running in the longitudinal direction of theroll of flat material and defining at least one substantially straightside section running to the outside at an angle to the longitudinaldirection of the continuous roll of flat material; creating continuousbevels along the edges of the roll of flat material running in thelongitudinal direction of the roll of flat material; separating stripsections from the continuous roll of flat material; rolling up eachstrip section into a bushing shape; and obtaining a finished fallingplain bushing bearing which does not need any additional machining tothe width after being rolled up into a bushing shape, but exhibits itsfinal varying bushing width.
 2. The process in accordance with claim 1,further comprising the steps of forming a multiple offset of theperipheral ends delineating the bushing width during the cutting of theside shape.
 3. The process in accordance with claim 1, furthercomprising the steps of forming two side sections, running parallel tothe longitudinal direction of the strip section and in alignment witheach other, and forming two side sections running to the outside at anangle to the longitudinal direction and delineating a broader sectionand forming one side section parallel to the longitudinal direction andconnecting the angled side sections to each other.
 4. The process inaccordance with claim 1, while still in the planar state, starting froma load impact joint, forming two side sections, running to the outsideat an angle to the longitudinal direction, and one side section isformed, running parallel to the longitudinal direction connecting theangled side sections to each other.
 5. The process in accordance withclaim 1, further comprising forming a tongue-like projection and amatching recess which can engage the projection in the load impact areaof the ends of the ribbon-shaped section of strip from which the bushingis rolled up, which ends are at least almost abutting.
 6. The process inaccordance with claim 5, wherein the forming step further comprises thestep of: forming the tongue-like projection centered along alongitudinal line of the strip section.
 7. The process in accordancewith claim 1, further comprising the step of coining the bevels at leastin sections.
 8. The process in accordance with claim 1, furthercomprising the steps of, prior to cutting the side shape and prior toseparating the strip sections, edging, profile rolling, and chasing thelongitudinal sides of the continuous roll of flat material.
 9. Theprocess in accordance with claim 1, further comprising the steps of,prior to rolling the sections of strip, coining an oil groove andforming lubricating holes.
 10. The process in accordance with claim 1,further comprising the step of, after the strip sections are rolled upinto the bushing shape, performing a ball-sizing calibration.
 11. Theprocess in accordance with claim 1, further comprising the step of,after rolling up the bushing, performing an outside draw calibration.12. The process in accordance with claim 1, further comprising the stepof cutting several continuous strips of flat material of lesser width,and varying in width in the longitudinal direction from one continuousroll of flat material of a primary width.
 13. The process in accordancewith claim 1, wherein the creating step is performed after the cuttingstep.
 14. The process in accordance with claim 1, wherein the creatingstep is performed before the separating step.
 15. The process inaccordance with claim 1, wherein the creating step further comprises thestep of: forming a first bevel along a portion of the ribbon shapedcontinuous roll by chasing before the cutting step.
 16. The process inaccordance with claim 15, wherein the creating step further comprisesthe step of: forming at least a second bevel along a portion of the sideshape by coining, the portion of the side shape formed in the cuttingstep.
 17. A process for manufacturing a rolled-up plain bearing bushingfrom a ribbon-shaped continuous roll of flat material, having a bushingwidth which varies over the length of the circumference, comprising thestep of: cutting a side shape from a ribbon-shaped continuous roll offlat material, so that a profile of varying width is formed, running inthe longitudinal direction of the roll of flat material and defining atleast one substantially straight side section running to the outside atan angle to the longitudinal direction of the continuous roll of flatmaterial.
 18. The process in accordance with claim 17, furthercomprising the step of: introducing a bevel along a portion of theribbon-shaped continuous roll of flat material before the cutting step.19. The process in accordance with claim 18, further comprising the stepof: forming a bevel along a second portion of the ribbon-shapedcontinuous roll of flat material after the cutting step.
 20. The processin accordance with claim 19, further comprising the step of: separatingstrip sections from the continuous roll of flat material after theforming step.